Unfortunately, seperate content builds are not feaseable with our current project setup. Yes, we love the opus codec, but it is not supported by Unity. The art has been entirely created by our artist from scratch without any upscaling filters applied to preexisting art.
Concerning your connection issues, you really should give the itch.io app or another download manager a try because it will allow you to resume incomplete downloads. We think this is the best way to deal with these kind of issues. On top of that, you will get automatic updates if you use the itch app.